@cmdcode/frost
v1.0.5
Published
Flexible, round-optimized schnorr threshold signatures for Bitcoin.
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FROST
Flexible round-optimized schnorr threshold signatures for Bitcoin.
How to Use
The FROST protocol specifies two rounds for producing a threshold signature.
Initial setup of parameters (using a trusted dealer):
This repository use a trusted dealer method for demonstration purposes. Feel free to use your own DKG protocol for generating and distributing shares.
import { create_key_group } from '@cmdcode/frost/lib'
import { random_bytes } from '@cmdcode/frost/util'
// Generate a random secret key and message.
const seckey = random_bytes(32).hex
const message = random_bytes(32).hex
// Configure the paramaters of the group.
const secrets = [ seckey ]
const threshold = 2
const share_max = 3
// Generate a group of secret shares.
const group = create_key_group(secrets, threshold, share_max)
Round 1 Example (nonce commitments):
Each member that is participating in the signing round must first create a nonce commitment:
import { create_commit_pkg } from '@cmdcode/frost/lib'
// Select a threshold (t) amount of shares and create nonce commitments.
const shares = group.shares.slice(0, threshold)
const commits = shares.map(e => create_commit_pkg(e))
Each member then distributes their nonce commitment to other members.
Round 2 Example (signing with secret shares):
Once all participating member commitments have been collected, we can now produce a partial signature:
import {
get_commit_pkg,
get_session_context,
sign_msg,
verify_partial_sig
} from '@cmdcode/frost/lib'
// Compute the context data for the signing session.
const ctx = get_session_ctx(group.pubkey, commits, message)
// Convert the share indices into iterable numbers.
const idx = ctx.indexes.map(i => Number(i) - 1)
// Collect a partial signature from each share.
const psigs = idx.map(i => {
const share = shares[i]
const commit = get_commit_pkg(commits, share)
const sig = sign_msg(ctx, share, commit)
if (!verify_partial_sig(ctx, commit, sig.pubkey, sig.psig)) {
throw new Error('sig share failed validation')
}
return sig
})
When the partial signatures have been collected, we can aggregate them into a full signature:
import { combine_partial_sigs, verify_final_sig } from '@cmdcode/frost/lib'
// Aggregate the partial signatures into a single signature.
const signature = combine_partial_sigs(ctx, psigs)
// Check that the signature is valid.
const is_valid = verify_final_sig(ctx, message, signature)
console.log('is valid:', is_valid)
Development and Testing
To run the test suite, use the following commands:
yarn test # For yarn.
npm run test # For NPM.
The test suite comes bundled with Bitcoin Core (located in test/bin
) for testing purposes. Depending on your computer architecture, you may have to replace these binaries with another version, or change the default configuration in test/tape.ts
.
There are code examples located in test/examples
for performing various protocols via FROST and DKG. You can run a test file via the following command:
yarn load test/example/<example_name>.ts
Feel free to check them out!
Resources
ZF FROST Book
A guide to the FROST protocol.
https://frost.zfnd.org/index.html
FROST draft specification
A draft specification of the FROST protocol from the IETF.
https://www.ietf.org/archive/id/draft-irtf-cfrg-frost-15.html
ZCash FROST GitHub
A rust implementation of the IETF FROST draft spec, in rust.
https://github.com/ZcashFoundation/frost
FROST BIP340
A draft implemenation of the FROST protocol for BIP340.
https://github.com/jesseposner/FROST-BIP340
Draft BIP for Secure DKG
A draft proposal for secure DKG in FROST, provided by Blockstream Research.
https://github.com/BlockstreamResearch/bip-frost-dkg
ROAST GitHub
A naive implementation of the ROAST protocol, written in rust.
https://github.com/robot-dreams/roast
FROST Whitepaper
The white-paper for FROST: Flexible Round-Optimized Schnorr Threshold Signatures
https://eprint.iacr.org/2020/852.pdf
ROAST Whitepaper
A white-paper for ROAST: Robust Asynchronous Schnorr Threshold Signatures.
https://eprint.iacr.org/2022/550.pdf